Draw phase-plane direction fields for the following equations and sketch the form you would expect the solution paths to take, starting from the points (x, v) = (1, 0), (0, 1), (–1, 0) and (0, –1) in each case:

dx dx (a) + - + x = 0 dt dt dx d.x (b) + + sgn(x) = 0 dr dt